Two-stage cooling system for chemical material cooling and control method thereof

Abstract

The application discloses a two-stage cooling system for chemical material cooling and a control method thereof, and belongs to the technical field of chemical industry. The two-stage cooling system is designed to solve the problem of energy waste caused by rough regulation and control of the existing cooling system. The two-stage cooling system comprises a primary refrigeration system, a secondary refrigeration system, a material cooling system, a flow detection component, and a temperature detection component. The two-stage cooling system for chemical material cooling and the control method thereof can monitor the inlet temperature of the material and the temperature between the two stages of heat exchangers by adding a material inlet temperature sensor at the inlet of the material to be cooled and adding a material inter-stage temperature sensor before the two stages of heat exchangers, so that the temperature of the cold source can be finely regulated and optimized, the cooling potential of the front stage is fully utilized, and the overall energy efficiency is higher.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a two-stage cooling system for cooling chemical materials and its control method. Background Technology

[0002] Many processes in chemical production involve intense heat release, requiring timely cooling to ensure precise and stable reaction temperatures. Traditional cooling methods utilize single-stage cooling systems, often relying on low-grade cold sources. However, prematurely consuming high-grade cold energy while materials are at high temperatures leads to a severe mismatch between the cold source grade and the cooling temperature, resulting in a decrease in the overall coefficient of performance (COP) and a significant increase in system energy consumption. Furthermore, single-stage cooling systems exhibit low temperature control accuracy when facing fluctuations in heat load.

[0003] To address the aforementioned issues, two-stage cooling systems are employed in some chemical engineering scenarios. Based on a phased, temperature-matched cooling approach, two-stage cooling systems theoretically possess higher energy efficiency potential. However, the drawbacks of two-stage cooling systems include: they typically only ensure the final outlet temperature of the material meets the standard, failing to finely control and optimize the cold source temperature of the two cooling loops (especially the first stage). This results in the cooling potential of the first stage not being fully utilized, forcing the system to consume additional high-grade cooling energy in the subsequent stage to compensate for the insufficient cooling effect of the first stage. This compensation mechanism essentially violates the core principle of thermodynamic grade matching, causing high-grade cooling energy to be ineffectively dissipated in unnecessary high-temperature ranges, severely degrading the overall energy efficiency of the system. Summary of the Invention

[0004] The purpose of this invention is to propose a two-stage cooling system and its control method for cooling chemical materials, which solves the problem of poor precision in cold source temperature control of existing cooling systems and has a high overall energy efficiency.

[0005] To achieve this objective, the present invention employs the following technical solution: A two-stage cooling system for cooling chemical materials includes: a primary refrigeration system comprising a primary evaporative cooling tower, a primary compressor, a primary evaporator, a primary internal cooling medium circulation pump, a primary cooling medium water tank, and a primary external cooling medium circulation pump; the primary evaporative cooling tower, the primary compressor, and the primary evaporator forming a primary refrigerant circuit; and the primary evaporator, the primary internal cooling medium circulation pump, and the primary cooling medium water tank forming a primary cooling medium circuit; a secondary refrigeration system comprising a secondary evaporative cooling tower, a secondary compressor, a secondary evaporator, a secondary internal cooling medium circulation pump, a secondary cooling medium water tank, and a secondary external cooling medium circulation pump; the secondary evaporative cooling tower, the secondary compressor, and the secondary evaporator forming a secondary refrigerant circuit; and the secondary evaporator, the secondary internal cooling medium circulation pump, and the secondary cooling medium water tank forming a secondary cooling medium circuit; and a material cooling system comprising a primary process condenser, a secondary process condenser, a primary cooling water inlet regulating valve, a secondary cooling water inlet regulating valve, a material inlet temperature sensor, a material interstage temperature sensor, and a material outlet temperature sensor. A cooling material circuit is provided between the process condenser and the secondary process condenser; the primary cooling medium water tank is connected to both ends of the primary process condenser, and the primary cooling medium external circulation pump is located between the primary cooling medium water tank and the primary process condenser; the secondary cooling medium water tank is connected to both ends of the secondary process condenser, and the secondary cooling medium external circulation pump is located between the secondary cooling medium water tank and the secondary process condenser; a flow detection component includes a primary header flow sensor and a secondary header flow sensor, the primary header flow sensor being located between the primary cooling medium water tank and the primary process condenser, and the secondary header flow sensor being located between the secondary cooling medium water tank and the secondary process condenser; and a temperature detection component includes a first temperature sensor for detecting the supply water temperature of the primary cooling system header, a second temperature sensor for detecting the return water temperature of the primary cooling system header, a third temperature sensor for detecting the supply water temperature of the secondary cooling system header, and a fourth temperature sensor for detecting the return water temperature of the secondary cooling system header.

[0006] In one preferred embodiment, the two-stage cooling system for cooling chemical materials includes one set of the material cooling systems; or, the two-stage cooling system for cooling chemical materials includes at least two sets of the material cooling systems, all of which are connected in parallel.

[0007] In one preferred embodiment, both the primary refrigeration system and the secondary refrigeration system are ammonia refrigeration systems.

[0008] On the other hand, the present invention adopts the following technical solution: A control method for a two-stage cooling system for cooling chemical materials, based on the aforementioned two-stage cooling system for cooling chemical materials, wherein one of the primary refrigeration system and the secondary refrigeration system is used to handle the high-temperature load, and the other of the primary refrigeration system and the secondary refrigeration system is used to handle the deep low-temperature load, and the minimum energy consumption E is optimized.

[0009] In one preferred embodiment, the control method includes the following steps: Step S1: Preset the primary liquid supply temperature T1 and the secondary liquid supply temperature T3; Step S2: Adjust the opening of the primary cooling water inlet regulating valve and the secondary cooling water inlet regulating valve to make the material outlet temperature reach the set value; Step S3: Monitor the return liquid temperature T2 of the primary header pipe, the return liquid temperature T4 of the secondary header pipe, and the cooling medium flow rate; calculate the actual total heat exchange at the terminal end Q. 实际 With the goal of minimizing total energy consumption E, optimization strategies are used to optimize the primary liquid supply temperature T1 and the secondary liquid supply temperature T3 respectively. Step S4: Control the operating parameters of the components in the dual-stage cooling system based on the optimization results of the primary liquid supply temperature T1 and the secondary liquid supply temperature T3. Step S5: Monitor the actual primary header return temperature T2, secondary header return temperature T4, and cooling medium flow rate, and calculate the actual total energy consumption E. 实际 Determine E 实际 Check if the difference ∆E between E and E meets the set value; if it does, continue execution; if it does not, proceed to step S3.

[0010] In one preferred embodiment, the formula for finding the minimum total system energy consumption E using a genetic algorithm is as follows: Where E is the total energy consumption of the system, T1 and T3 are decision variables, W1 is the energy consumption of the first-stage compressor, W2 is the energy consumption of the second-stage compressor, P1 is the power of the internal circulation pump of the first-stage cooling circulation system, P2 is the power of the external circulation pump of the first-stage cooling circulation system, P3 is the power of the internal circulation pump of the second-stage cooling circulation system, and P4 is the power of the external circulation pump of the second-stage cooling circulation system.

[0011] In one preferred embodiment, the energy consumption of the first-stage compressor is calculated using the formula W1=Q1 / COP1, where W1 is the power (kW) of the first-stage compressor and COP1 is the coefficient of performance (COP1) of the first-stage compressor; the energy consumption of the second-stage compressor is calculated using the formula W2=Q2 / COP2, where W2 is the power (kW) of the second-stage compressor and COP2 is the coefficient of performance (COP2) of the second-stage compressor.

[0012] In one preferred embodiment, the total heat exchange Q 总 =Q1+Q2, where, , Q is the heat exchange capacity (kW), C is the specific heat capacity of the cooling medium (kJ / (kg•℃)), and q v Cooling medium volumetric flow rate (m³) 3 / h), ρ is the density of the cooling medium (kg / m³) 3 ).

[0013] In one preferred embodiment, the formula for calculating the power consumption of the water pump is: Where P is the power of the water pump (kW), q v Where H is the flow rate of the cooling medium, g is the pump head (m), ŋ is the acceleration due to gravity (N / kg), and ŋ is the pump efficiency (%). ; ; ; .

[0014] In one preferred embodiment, the theoretical cooling medium flow rate calculation formula for the primary main pipe flow sensor monitoring point is as follows: The theoretical cooling medium flow rate calculation formula for the monitoring point of the secondary main pipe flow sensor is as follows: .

[0015] The present invention discloses a two-stage cooling system for cooling chemical materials. A material inlet temperature sensor is added at the inlet of the material to be cooled, and an interstage temperature sensor is added before the two-stage heat exchangers to monitor the material inlet temperature and the interstage temperature. This allows for precise control and optimization of the cold source temperature, fully utilizing the cooling potential of the preceding stage. By monitoring and controlling the water temperature of the two-stage cooling system, the energy waste caused by the crude control of existing two-stage cooling systems in the chemical industry is solved, resulting in low system energy consumption.

[0016] The present invention discloses a control method for a two-stage cooling system for cooling chemical materials. By establishing a system energy consumption collaborative optimization model, the method seeks the global minimum energy consumption operating point, thereby achieving the optimization of the energy efficiency of the two-stage cooling system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a two-stage cooling system for cooling chemical materials provided in a specific embodiment of the present invention; Figure 2 This is a schematic diagram of the control device provided in a specific embodiment of the present invention.

[0018] In the picture: 1. Primary refrigeration system; 2. Secondary refrigeration system; 11. Primary evaporative cooling tower; 12. Primary compressor; 13. Primary evaporator; 14. Primary cooling medium internal circulation pump; 15. Primary cooling medium water tank; 16. Primary cooling medium external circulation pump; 21. Secondary evaporative cooling tower; 22. Secondary compressor; 23. Secondary evaporator; 24. Secondary cooling medium internal circulation pump; 25. Secondary cooling medium water tank; 26. Secondary cooling medium external circulation pump; 31. Primary process condenser; 32. Secondary process condenser; 33. Primary cooling water inlet regulating valve; 34. Secondary cooling water inlet regulating valve; 35. Material inlet temperature sensor; 36. Material interstage temperature sensor; 37. Material outlet temperature sensor; 41. Primary main pipe flow sensor; 42. Secondary main pipe flow sensor; 51. First temperature sensor; 52. Second temperature sensor; 53. Third temperature sensor; 54. Fourth temperature sensor. Detailed Implementation

[0019] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0022] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0024] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0025] This embodiment discloses a two-stage cooling system for cooling chemical materials and its control method, such as Figure 1 As shown, the two-stage cooling system for cooling chemical materials includes a primary refrigeration system 1, a secondary refrigeration system 2, a material cooling system, a flow detection component, and a temperature detection component.

[0026] The primary refrigeration system 1 includes a primary evaporative cooling tower 11, a primary compressor 12, a primary evaporator 13, a primary internal cooling medium circulation pump 14, a primary cooling medium water tank 15, and a primary external cooling medium circulation pump 16. The primary evaporative cooling tower 11, the primary compressor 12, and the primary evaporator 13 form a primary refrigerant circuit, and the primary evaporator 13, the primary internal cooling medium circulation pump 14, and the primary cooling medium water tank 15 form a primary cooling medium circuit.

[0027] The secondary refrigeration system 2 includes a secondary evaporative cooling tower 21, a secondary compressor 22, a secondary evaporator 23, a secondary internal circulation pump for cooling medium 24, a secondary cooling medium water tank 25, and a secondary external circulation pump for cooling medium 26. The secondary evaporative cooling tower 21, the secondary compressor 22, and the secondary evaporator 23 form a secondary refrigerant circuit, and the secondary evaporator 23, the secondary internal circulation pump for cooling medium 24, and the secondary cooling medium water tank 25 form a secondary cooling medium circuit.

[0028] The material cooling system includes a primary process condenser 31, a secondary process condenser 32, a primary cooling water inlet regulating valve 33, a secondary cooling water inlet regulating valve 34, a material inlet temperature sensor 35, a material interstage temperature sensor 36, and a material outlet temperature sensor 37. A cooling material loop is provided between the primary process condenser 31 and the secondary process condenser 32. The primary cooling medium tank 15 is connected to both ends of the primary process condenser 31, and the primary cooling medium external circulation pump 16 is located between the primary cooling medium tank 15 and the primary process condenser 31. The secondary cooling medium tank 25 is connected to both ends of the secondary process condenser 32, and the secondary cooling medium external circulation pump 26 is located between the secondary cooling medium tank 25 and the secondary process condenser 32.

[0029] The flow detection assembly includes a primary main pipe flow sensor 41 and a secondary main pipe flow sensor 42. The primary main pipe flow sensor 41 is located between the primary cooling medium water tank 15 and the primary process condenser 31, and the secondary main pipe flow sensor 42 is located between the secondary cooling medium water tank 25 and the secondary process condenser 32.

[0030] The temperature detection assembly includes a first temperature sensor 51, a second temperature sensor 52, a third temperature sensor 53, and a fourth temperature sensor 54. The first temperature sensor 51 is used to detect the water supply temperature of the main pipe of the primary cooling system, the second temperature sensor 52 is used to detect the water return temperature of the main pipe of the primary cooling system, the third temperature sensor 53 is used to detect the water supply temperature of the main pipe of the secondary cooling system, and the fourth temperature sensor 54 is used to detect the water return temperature of the main pipe of the secondary cooling system.

[0031] Figure 1 The area within the dashed box represents the final process side, while the area outside the dashed box represents the cold source side of the cooling station. This two-stage cooling system for chemical materials incorporates a material inlet temperature sensor 35 at the inlet of the material being cooled and an interstage material temperature sensor 36 before the two-stage heat exchangers to monitor the material inlet temperature and the interstage cooling temperature. This allows for precise control and optimization of the cold source temperature, fully utilizing the cooling potential of the preceding stage and solving the problem of existing cooling systems being forced to consume additional high-grade cooling capacity in the subsequent stage to compensate for the cooling effect of the preceding stage. Overall, this results in a higher energy efficiency level.

[0032] This two-stage cooling system for chemical materials can consist of only one cooling system for high efficiency, or it can include at least two parallel cooling systems capable of simultaneously cooling large quantities of materials, providing a superior user experience. All cooling systems have identical internal structures, ensuring consistent cooling performance across all systems.

[0033] To address the limitation of existing fluorinated refrigeration + cooling water systems that only operate at temperatures ≥30℃, this two-stage cooling system for chemical materials utilizes ammonia refrigeration in both its primary (Stage 1) and secondary (Stage 2) systems. This meets the stringent requirements of the chemical industry for deep cryogenic temperatures below 0℃ and large temperature differences (ΔT > 50℃). Primary system 1 handles the high-temperature load, while secondary system 2 handles the deep cryogenic load. The division between "high-temperature load" and "low-temperature load" is not specifically defined and can be determined based on actual usage requirements. This two-stage cooling system for chemical materials broadens the applicable temperature range, meeting the process requirements for -30℃ cryogenic outlets. It fills the technological gap in energy-saving control of two-stage ammonia refrigeration in the cryogenic chemical field, offering wider applicability and stronger product competitiveness.

[0034] Based on the above control method for a two-stage cooling system for chemical materials: one of the primary refrigeration system 1 and the secondary refrigeration system 2 is used to handle the high-temperature load, and the other of the primary refrigeration system 1 and the secondary refrigeration system 2 is used to handle the deep low-temperature load, and the minimum energy consumption E is optimized.

[0035] This control method seeks the global minimum energy consumption operating point by establishing a system energy consumption collaborative optimization model, thereby achieving the optimal energy efficiency of the two-stage cooling system.

[0036] like Figure 2 As shown, the control device of the two-stage cooling system includes an optimization layer, an execution layer, a monitoring layer, and a judgment layer. The optimization layer can establish an energy consumption calculation model and a setting model for the compressor, water pump, etc. The execution layer is used to execute PID control. The monitoring layer can calculate the actual total energy consumption E based on the actual measured temperature and flow rate. The judgment layer is used to determine whether the deviation between the actual total energy consumption and the predicted total energy consumption meets expectations.

[0037] In this embodiment, the control device can be a centralized or distributed controller. For example, the controller can be a single microcontroller or a combination of multiple distributed microcontrollers. The microcontroller can run a control program to control the two-stage cooling system to achieve its function.

[0038] The control method includes the following steps: Step S1: Preset the primary liquid supply temperature T1 and the secondary liquid supply temperature T3 within a reasonable range.

[0039] Step S2, monitoring t实际 , and The opening of the primary cooling water inlet regulating valve 33 and the secondary cooling water inlet regulating valve 34 is adjusted by PID (Proportional Integral Derivative) control system to make the material outlet temperature the set value.

[0040] Step S3: Monitor the return liquid temperature T2 of the primary header pipe, the return liquid temperature T4 of the secondary header pipe, and the cooling medium flow rate; calculate the actual total heat exchange at the terminal end Q. 实际 With the goal of minimizing total energy consumption E, optimization strategies are used to optimize the primary liquid supply temperature T1 and the secondary liquid supply temperature T3 respectively.

[0041] Step S4: Send the optimization results T1 and T3 to the PLC execution layer, that is, control the working parameters of the components in the two-stage cooling system according to the optimization results of the primary liquid supply temperature T1 and the secondary liquid supply temperature T3.

[0042] Step S5: Monitor the actual primary header return temperature T2, secondary header return temperature T4, and cooling medium flow rate, and calculate the actual total energy consumption E. 实际 Determine E 实际 Check if the difference ∆E between E and E meets the set value. If it does, continue execution; otherwise, go to step S3 until ∆E meets the set value.

[0043] This control method employs a two-layer control strategy. In the basic control layer, the valve opening is controlled through a PID closed-loop control to ensure the material outlet temperature. The system stabilizes at the setpoint; in the dynamic optimization layer, the actual total heat exchange Q of the system is calculated based on real-time data collected (T1, T2, T3, T4, qv1, and qv2). 总 (Q) 总 =Q1+Q2), by dynamically allocating the heat exchange between the primary and secondary stages (Q=Q1+Q2), the energy coupling relationship of the two-stage cooling system is established to minimize the total energy consumption E of the system. The liquid supply temperature setpoint (T1,T3) is dynamically adjusted using an optimization algorithm. The optimization results are effectively implemented through iterative verification (∆E≤threshold). A multi-equipment collaborative energy consumption model is constructed to couple the energy consumption of the refrigeration compressor system (W1, W2), the energy consumption of the internal circulation pump group (P1, P2), and the energy consumption of the external circulation pump group (P3, P4).

[0044] In order to find the global minimum energy consumption operating point and optimize the energy efficiency of the two-stage cooling system, it is first necessary to establish a calculation model of the main energy-consuming equipment of the refrigeration system.

[0045] According to the formula for calculating total heat exchange, Q = C•q v•ρ•∆t / 3600, Q is the heat exchange capacity (kW), C is the specific heat capacity of the cooling medium (kJ / (kg•℃)), q v Cooling medium volumetric flow rate (m³) 3 / h), ρ is the density of the cooling medium (kg / m³) 3 ∆t is the temperature difference between the supply and return water (°C).

[0046] The formula for calculating the supply and return water temperature difference ∆t is as follows: , among which, T h T represents the return temperature of the cooling medium (°C). g The supply temperature of the cooling medium (°C).

[0047] Since this two-stage cooling system involves two separate cooling stages, it is necessary to solve for the heat exchange of each stage separately, i.e., the total heat exchange Q. 总 =Q1+Q2, where the heat exchange capacity of the first-stage heat exchanger is The heat exchange capacity of the secondary heat exchanger is .

[0048] The cooling capacity required by the compressor is the sum of the heat exchange at all terminals. The compressor power is calculated using the formula W=Q / COP, where W is the compressor power (kW) and COP is the coefficient of performance.

[0049] In this embodiment, the power required by the first-stage compressor 12 is W1=Q1 / COP1, where W1 is the power of the first-stage compressor 12 (kW) and COP1 is the coefficient of performance of the first-stage compressor 12; the power required by the second-stage compressor 22 is W2=Q2 / COP2, where W2 is the power of the second-stage compressor 22 (kW) and COP2 is the coefficient of performance of the second-stage compressor 22.

[0050] When the heat exchange capacity and the heat exchange temperature difference are known, the formula for calculating the cooling medium flow rate is: Therefore, the theoretical cooling medium flow rate calculation formula for monitoring point 41 of the primary main pipe flow sensor is: The theoretical cooling medium flow rate calculation formula for the 42 monitoring points of the secondary main pipe flow sensor is as follows: .

[0051] The formula for calculating the power consumption of a water pump is: Where P is the power of the water pump (kW), q v denoted as , where H is the pump head (m), g is the gravitational acceleration (N / kg), and ŋ is the pump efficiency (%).

[0052] The two-stage cooling system includes internal and external circulation pumps. The power of the internal circulation pump in the first-stage cooling circulation system is P1, the power of the external circulation pump in the first-stage cooling circulation system is P2, the power of the internal circulation pump in the second-stage cooling circulation system is P3, and the power of the external circulation pump in the second-stage cooling circulation system is P4. This control method incorporates the energy consumption of the coupled two-stage refrigeration compressor system (W1, W2) and the energy consumption of the dual-cycle pump system (P1, P2, P3, and P4) into a unified energy consumption model (E=∑W+∑P), breaking through the limitations of traditional single-device independent optimization and quantifying the energy consumption interaction mechanism between the compressor and the pump system. By dynamically allocating the heat load (Q=Q1+Q2), it solves the problem of high-grade cooling capacity waste caused by the imbalance of cooling capacity distribution between the front and rear stages, directly reducing the total system energy consumption.

[0053] To address the challenges of nonlinear optimization caused by strong coupling of multiple systems, this paper proposes a four-layer constraint system using temperature parameters as optimization variables. This system encompasses thermal balance, temperature boundaries, minimum temperature difference, and equipment performance. Global optimization is then performed using a genetic algorithm, effectively solving the problem of strong coupling of multiple systems that is difficult to handle with traditional single-equipment optimization methods. Furthermore, this approach addresses the issue of mismatch between heat and cold source grades caused by independent equipment optimization, preventing the ineffective dissipation of high-grade cooling capacity in high-temperature regions and improving the overall energy efficiency of the system.

[0054] In this embodiment, considering the strong nonlinear coupling characteristics between the refrigeration compressor system and the pump system (the compressor COP changes nonlinearly with temperature, and the pump power consumption and flow rate are cubic), a genetic algorithm with a population global search mechanism is used to handle this type of non-convex optimization problem, thus solving the problem that traditional gradient optimization algorithms are prone to getting trapped in local optima.

[0055] Because the energy efficiency coupling model involves the cross-influence of six-dimensional energy consumption variables (W1 / W2 / P1 / P2 / P3 / P4) and two-dimensional temperature decision variables (T1, T3), and because there are complex thermodynamic relationships among these variables (such as changes in T1 simultaneously affecting Q1, W1, and q), v1 (P1) Genetic algorithms can efficiently search for the global optimum in this eight-dimensional solution space. They can overcome complex constraints such as compressor COP nonlinearity and the cubic relationship between pump power consumption and flow rate, avoid getting trapped in local optima, and accurately search for the global minimum energy consumption point (min E).

[0056] In this embodiment, the total energy consumption of the entire system is defined as E. The formula for finding the minimum total energy consumption E of the system using a genetic algorithm is as follows: Where E is the total energy consumption of the system, T1 and T3 are decision variables, W1 is the energy consumption of the first-stage compressor 12, W2 is the energy consumption of the second-stage compressor 22, P1 is the energy consumption of the internal circulation pump of the first-stage cooling circulation system, P2 is the energy consumption of the external circulation pump of the first-stage cooling circulation system, P3 is the energy consumption of the internal circulation pump of the second-stage cooling circulation system, and P4 is the energy consumption of the external circulation pump of the second-stage cooling circulation system.

[0057] In order to find the optimal solution for system energy efficiency, this control method seeks the minimum value of total system energy consumption E by optimizing the inlet and outlet temperatures of the cooling medium; it achieves cross-device collaborative optimization through dynamic heat load allocation (Q=Q1+Q2) and uses genetic algorithms to solve multi-system coupling problems that traditional single-device optimization cannot handle.

[0058] Based on the above, this control method optimizes the minimum energy consumption E by dynamically adjusting the cold source temperature (T1, T3) and setting four constraints in the solver genetic algorithm, while verifying the accuracy of the optimization results through an iterative mechanism.

[0059] The four constraints are heat load balance constraint, heat transfer direction constraint, minimum temperature difference constraint, and equipment performance constraint.

[0060] First, heat load balance constraints: Where Q is the total system heat load, a fixed value calculated based on measured data; Q1 and Q2 are dynamically allocated heat load components.

[0061] Second, heat transfer direction constraint: in, This represents the minimum inlet temperature of all materials being cooled. The minimum value set for the temperature between all cooling stages. Set the minimum temperature for all outlets of the cooled materials. , and Given the temperature parameters. Since some cooling processes have no temperature requirement for t´, calculate the minimum value of t´ for the intermediate temperature only.

[0062] Third, minimum temperature difference constraint: , In the formula: ΔTmin is the minimum temperature difference to ensure heat exchange efficiency.

[0063] Fourth, equipment performance constraints: the compressor and water pump frequencies are within their allowable ranges; through optimization algorithms, T1 and T3 when the total energy consumption of the system is minimized are calculated and sent to the execution layer.

[0064] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A two-stage cooling system for cooling chemical materials, characterized in that, include: The primary refrigeration system (1) includes a primary evaporative cooling tower (11), a primary compressor (12), a primary evaporator (13), a primary cooling medium internal circulation pump (14), a primary cooling medium water tank (15), and a primary cooling medium external circulation pump (16). The primary evaporative cooling tower (11), the primary compressor (12), and the primary evaporator (13) form a primary refrigerant circuit, and the primary evaporator (13), the primary cooling medium internal circulation pump (14), and the primary cooling medium water tank (15) form a primary cooling medium circuit. The secondary refrigeration system (2) includes a secondary evaporative cooling tower (21), a secondary compressor (22), a secondary evaporator (23), a secondary cooling medium internal circulation pump (24), a secondary cooling medium water tank (25), and a secondary cooling medium external circulation pump (26). The secondary evaporative cooling tower (21), the secondary compressor (22), and the secondary evaporator (23) form a secondary refrigerant circuit, and the secondary evaporator (23), the secondary cooling medium internal circulation pump (24), and the secondary cooling medium water tank (25) form a secondary cooling medium circuit. The material cooling system includes a primary process condenser (31), a secondary process condenser (32), a primary cooling water inlet regulating valve (33), a secondary cooling water inlet regulating valve (34), a material inlet temperature sensor (35), a material interstage temperature sensor (36), and a material outlet temperature sensor (37). A cooling material circuit is provided between the primary process condenser (31) and the secondary process condenser (32). The primary cooling medium water tank (15) is connected to both ends of the primary process condenser (31), and the primary cooling medium external circulation pump (16) is located between the primary cooling medium water tank (15) and the primary process condenser (31). The secondary cooling medium water tank (25) is connected to both ends of the secondary process condenser (32), and the secondary cooling medium external circulation pump (26) is located between the secondary cooling medium water tank (25) and the secondary process condenser (32). The flow detection assembly includes a primary main pipe flow sensor (41) and a secondary main pipe flow sensor (42). The primary main pipe flow sensor (41) is disposed between the primary cooling medium tank (15) and the primary process condenser (31), and the secondary main pipe flow sensor (42) is disposed between the secondary cooling medium tank (25) and the secondary process condenser (32); and, The temperature detection assembly includes a first temperature sensor (51) for detecting the supply water temperature of the main pipe of the primary cooling system, a second temperature sensor (52) for detecting the return water temperature of the main pipe of the primary cooling system, a third temperature sensor (53) for detecting the supply water temperature of the main pipe of the secondary cooling system, and a fourth temperature sensor (54) for detecting the return water temperature of the main pipe of the secondary cooling system.

2. The two-stage cooling system for cooling chemical materials according to claim 1, characterized in that, The two-stage cooling system for cooling chemical materials includes one set of the material cooling systems; or, the two-stage cooling system for cooling chemical materials includes at least two sets of the material cooling systems, with all the material cooling systems connected in parallel.

3. The two-stage cooling system for cooling chemical materials according to claim 1 or 2, characterized in that, Both the primary refrigeration system (1) and the secondary refrigeration system (2) are ammonia refrigeration systems.

4. A control method for a two-stage cooling system for cooling chemical materials, based on any one of claims 1 to 3, characterized in that, One of the primary refrigeration system (1) and the secondary refrigeration system (2) is used to handle the high-temperature load, and the other of the primary refrigeration system (1) and the secondary refrigeration system (2) is used to handle the deep low-temperature load, and the minimum energy consumption E is optimized.

5. The control method for a two-stage cooling system for cooling chemical materials according to claim 4, characterized in that, The control method includes the following steps: Step S1: Preset the primary liquid supply temperature T1 and the secondary liquid supply temperature T3; Step S2: Adjust the opening of the primary cooling water inlet regulating valve (33) and the secondary cooling water inlet regulating valve (34) to make the material outlet temperature reach the set value; Step S3: Monitor the return liquid temperature T2 of the primary header pipe, the return liquid temperature T4 of the secondary header pipe, and the cooling medium flow rate; calculate the actual total heat exchange at the terminal end Q. 实际 With the goal of minimizing total energy consumption E, optimization strategies are used to optimize the primary liquid supply temperature T1 and the secondary liquid supply temperature T3 respectively. Step S4: Control the operating parameters of the components in the dual-stage cooling system based on the optimization results of the primary liquid supply temperature T1 and the secondary liquid supply temperature T3. Step S5: Monitor the actual primary header return temperature T2, secondary header return temperature T4, and cooling medium flow rate, and calculate the actual total energy consumption E. 实际 Determine E 实际 Check if the difference ∆E between E and E meets the set value; if it does, continue execution; if it does not, proceed to step S3.

6. The control method for a two-stage cooling system for cooling chemical materials according to claim 4, characterized in that, The formula for finding the minimum total energy consumption E of the system using a genetic algorithm is as follows: ； Where E is the total energy consumption of the system, T1 and T3 are decision variables, W1 is the energy consumption of the first-stage compressor (12), W2 is the energy consumption of the second-stage compressor (22), P1 is the power of the internal circulation pump of the first-stage cooling circulation system, P2 is the power of the external circulation pump of the first-stage cooling circulation system, P3 is the power of the internal circulation pump of the second-stage cooling circulation system, and P4 is the power of the external circulation pump of the second-stage cooling circulation system.

7. The control method for a two-stage cooling system for cooling chemical materials according to claim 6, characterized in that, The energy consumption calculation formula of the first-stage compressor (12) is W1=Q1 / COP1, where W1 is the power (kW) of the first-stage compressor (12) and COP1 is the coefficient of performance of the first-stage compressor (12). The energy consumption of the secondary compressor (22) is calculated using the formula W2=Q2 / COP2, where W2 is the power (kW) of the secondary compressor (22) and COP2 is the coefficient of performance of the secondary compressor (22).

8. The control method for a two-stage cooling system for cooling chemical materials according to claim 7, characterized in that, Total heat exchange Q 总 =Q1+Q2, where, , Q is the heat exchange capacity (kW), C is the specific heat capacity of the cooling medium (kJ / (kg•℃)), and qv is the volumetric flow rate of the cooling medium (m³ / s). 3 / h), ρ is the density of the cooling medium (kg / m³) 3 ).

9. The control method for a two-stage cooling system for cooling chemical materials according to claim 6, characterized in that, The formula for calculating the power consumption of a water pump is: ； Where P is the power of the water pump (kW), q v Where H is the flow rate of the cooling medium, g is the pump head (m), ŋ is the acceleration due to gravity (N / kg), and ŋ is the pump efficiency (%). ； ； ； 。 10. The control method for a two-stage cooling system for cooling chemical materials according to claim 9, characterized in that, The theoretical cooling medium flow rate calculation formula for the monitoring point of the primary main pipe flow sensor (41) is as follows: ； The theoretical cooling medium flow rate calculation formula for the monitoring point of the secondary main pipe flow sensor (42) is as follows: 。

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